There has always been a need in the railroad industry for ties with provisions to maximize resistance to motion along the tie length dimension. Such motion occurs in response to forces applied by weather conditions, and by the passage of trains along the rails. The problem of "tie movement" is most realized in areas where the rails curve. The rails in such areas are subjected to substantial lateral forces from the trains moving around the turns. Ties are also additionally subjected to forces applied by the rails themselves as they expand and contract in cold and warm weather conditions. The problem is amplified with the new "ribbon" rails that extend for substantial distances without joints.
One solution to the problem of lateral track movement is the provision for more railroad ties and closer spacing in areas where the track curves. This is not economically effective as railroad ties are becoming increasingly expensive.
The above problem is addressed in U.S. Pat. No. 1,888,287 to Prot which discloses a "ferro-concrete rail-way sleeper". The configuration of the tie includes an enlarged foot used to distribute vertical loading and minimize pressure on the ground surface. The tie is hollow along its length and includes a substantially rectangular central cross section adjacent the areas between rail mounting surfaces thereof. Webbing is provided at the rail mounting surfaces extending angularly downward from the rail mounting surfaces to the widened foot. Resistance to "side stresses" is claimed to be increased by provision of diverging ribs provided at the end portions of the sleeper.
Another attempted solution to the above problem is found in U.S. Pat. No. 1,720,473 to Habicht which discloses a railroad tie with a specific configuration intended to hold position within ballast. This tie construction includes a substantially triangular cross sectional configuration in which the top, flat surface of the tie represents one side of the triangular cross sectional configuration. Thus, the side walls converge downwardly in areas of the tie with the exception of those areas mounting the rails. It is stated that this form of tie configuration will afford a more uniform distribution of load on the surrounding ballast and will retain its position within the ballast.
U.S. Pat. No. 530,778 to Ingersoll discloses a tie configuration that is approximately opposite in cross sectional configuration to the Habicht reference discussed above. Here, end and central side surfaces of the tie diverge from the top surface to an enlarged foot at the bottom portion of the tie. Again, this configuration is claimed to effectively prevent endwise movement of the ties.
While the above ties may indeed improve traction and distribution of load, it remains desirable to obtain maximum resistance to lateral tie movement, especially when ties are used in conjunction with elongated, seamless "ribbon" rails. In doing so, it is desirable to obtain maximum traction of such ties within the aggregate forming the roadbed. Thus, it is the primary objective of the present invention to provide a tie configuration of economically feasible construction and that will provide maximum grip within a prepared aggregate ballast.